Interpreting energy expenditure for anaerobic exercise and recovery: an anaerobic hypothesis

Energy expenditure during and after exercise is composed of aerobic and anaerobic bioenergetics and the energy demands of aerobic recovery. Current attempts to measure energy expenditure include an exercise oxygen uptake + oxygen debt (EPOC) measurement or, an oxygen deficit + exercise oxygen uptake measurement. This investigation illustrates how oxygen debt and oxygen deficit interpretation can effect a total energy expenditure measurement. It was hypothesized that the total energy expenditure for several intermittent bouts of exercise and recovery would be greater than for one bout of continuous exercise and recovery when equivalent work was compared. Exercise was performed under low-intensity and high-intensity conditions. Both oxygen debt and oxygen deficit methodology resulted in similar energy expenditure measurements for both intermittent and continuous exercise. This implies little to no recovery energy demand or considerable methodology errors. Differences in total energy expenditure were found when the oxygen deficit and parts of the oxygen debt (EPOC) were considered separate and independent (p < 0.05). These differences can be accounted for when the data are interpreted utilizing thermodynamic (2nd law) and engineering (in-series efficiency) concepts rather than the heat equivalent of carbohydrate oxidation (20.9 kJ equals one liter of O2). It is suggested that while oxygen uptake provides an excellent representation of aerobic metabolism during exercise and recovery, oxygen uptake may be an inadequate measure of the energetics of lactate production (fermentation). In application, energy expenditure differences appear realistic only for high-intensity, intermittent exercise rather than lower intensity exercise.